class LockFixture(fixtures.Fixture):
"""External locking fixture.
This fixture is basically an alternative to the synchronized decorator with
the external flag so that tearDowns and addCleanups will be included in
the lock context for locking between tests. The fixture is recommended to
be the first line in a test method, like so::
def test_method(self):
self.useFixture(LockFixture)
...
or the first line in setUp if all the test methods in the class are
required to be serialized. Something like::
class TestCase(testtools.testcase):
def setUp(self):
self.useFixture(LockFixture)
super(TestCase, self).setUp()
...
This is because addCleanups are put on a LIFO queue that gets run after the
test method exits. (either by completing or raising an exception)
"""
def __init__(self, name, lock_file_prefix=None):
self.mgr = lockutils.lock(name, lock_file_prefix, True)

class _InterProcessLock(object):
"""Lock implementation which allows multiple locks, working around
issues like bugs.debian.org/cgi-bin/bugreport.cgi?bug=632857 and does
not require any cleanup. Since the lock is always held on a file
descriptor rather than outside of the process, the lock gets dropped
automatically if the process crashes, even if __exit__ is not executed.
There are no guarantees regarding usage by multiple green threads in a
single process here. This lock works only between processes. Exclusive
access between local threads should be achieved using the semaphores
in the @synchronized decorator.
Note these locks are released when the descriptor is closed, so it's not
safe to close the file descriptor while another green thread holds the
lock. Just opening and closing the lock file can break synchronisation,
so lock files must be accessed only using this abstraction.
"""
def __init__(self, name):
self.lockfile = None
self.fname = name
def __enter__(self):
self.lockfile = open(self.fname, 'w')